Vehicle control system and method

ABSTRACT

Embodiments of the present invention provide a motor vehicle control system for selecting and/or determining a driving surface and for controlling a plurality of vehicle subsystems to operate in a plurality of subsystem control modes in dependence on the selected/determined driving surface, the system being operable in a manual control mode selection condition in which a user is able to select said driving surface and an automatic control mode selection condition in which the system is configured to select said driving surface automatically, wherein the vehicle control system is provided with a memory arranged to memorize a last selected control mode that was selected prior to vehicle de-activation or key-off when operating in the automatic control mode selection condition, and upon the next subsequent vehicle activation or key-on, the system is configured to continue operating in the memorized control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place.

INCORPORATION BY REFERENCE

The entire contents of co-pending UK patent application numbers GB1111288.5, GB1211910.3 and GB1202427.9, UK patents GB2325716, GB2308415, GB2341430, GB2382158 and GB82381597 and US2003/0200016 are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a vehicle control system for one or more vehicle subsystems and to a method of controlling one or more vehicle subsystems.

BACKGROUND

It is known to provide a vehicle having a plurality of subsystems which can be operated in different configurations to suit different driving conditions. For example, automatic transmissions may be controlled in a variety of modes such as sport, manual, winter or economy. In each mode, subsystem control parameters such as accelerator pedal response and conditions under which changes between gear ratios take place may be modified so as to suit the conditions of the terrain or the particular taste of the driver. It is also known to provide air suspensions with on-road and off-road modes. Stability control systems can be operated at reduced activity in certain modes so as to give the driver more direct control, and power steering systems can be operated in different modes to provide a varying level of assistance depending on driving conditions.

In a known vehicle control system allowing selection of control modes optimised for different driving conditions, mode selection is entirely manual. The control system (which may also be referred to as a terrain response (TR) control system) responds to a user request for operation in a given control mode according to the position of a control knob. If the control knob has been left in a given mode (such as a grass/gravel/snow (GGS) mode) at key-off then the control system will assume the GGS mode at the next key-on, unless the control knob has been adjusted. Thus the position of the control knob determines the control mode that will be assumed by the controller.

Embodiments of the present invention have automatic mode selection functionality and may operate as described elsewhere herein. Embodiments of the invention may for example employ a multi-stable knob for mode selection, optionally of the kind described herein. In some embodiments the physical position of the knob is not indicative of selected mode. In embodiments having a rotatable knob the knob may be rotated through an angle greater than 360°.

It is to be understood that in some embodiments of the present invention the control system is able to determine confidently the type of terrain over which the vehicle is moving and determine the most appropriate control mode in a relatively short distance of travel (approximately less than two car lengths in some embodiments). When a vehicle moves from rest following key-on, the control system can therefore determine the most appropriate terrain relatively quickly and be ready to command a change in selected mode if required.

The applicant has recognised that since the most appropriate mode may be determined relatively quickly, the vehicle speed may be relatively low when the determination has been made. Furthermore, whether or not the speed is low, it may be possible to command the change relatively soon after the vehicle commences movement. A user of the vehicle may be particularly sensitive to vehicle motion and response of the vehicle to control inputs such as accelerator pedal input. If the control system commands the change as soon as it has determined that a change is needed, immediately or soon after starting, a user may perceive that a change in vehicle response has taken place and may perceive the change as a fault. The change may be detrimental to vehicle composure and user enjoyment.

Furthermore, if a user moves a vehicle between forwards and reverse gears directly after key-on, a change in selected mode may take place as a user changes vehicle direction. The user may readily detect the change, and again may perceive the change in behaviour as a fault.

It is desirable to provide an improved control system for a motor vehicle operable in different configurations.

Statement of the Invention

Embodiments of the invention may be understood with reference to the appended claims.

Aspects of the present invention provide a control system, a vehicle and a method.

Control systems according to embodiments of the present invention are suitable for a range of different vehicles including conventional engine-only vehicles, electric vehicles, and/or hybrid electric vehicles.

In one aspect of the invention for which protection is sought there is provided a motor vehicle control system for selecting and/or determining a driving surface and for controlling a plurality of vehicle subsystems to operate in a plurality of subsystem configuration or control modes in dependence on the selected/determined driving surface, the system being operable in a manual operating mode in which a user is able to select said driving surface and an automatic operating mode in which the system is operable to select said driving surface automatically, wherein the vehicle control system is provided with a memory arranged to memorise a last selected driving surface and/or subsystem configuration mode and/or control mode that was selected prior to vehicle de-activation or key-off, and upon the next subsequent vehicle activation or key-on, the system is configured to continue operating in the same subsystem configuration mode and/or control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in subsystem configuration mode and/or control mode to take place.

The automatic mode may also be referred to as an automatic operating mode or automatic control mode selection condition. The manual mode may also be referred to as a manual operating mode or control mode selection condition.

In a further aspect of the invention for which protection is sought there is provided a motor vehicle control system for selecting and/or determining a driving surface and for controlling a plurality of vehicle subsystems to operate in a plurality of subsystem control modes in dependence on the selected/determined driving surface, the system being operable in a manual control mode selection condition in which a user is able to select said driving surface and an automatic control mode selection condition in which the system is operable to select said driving surface automatically, wherein the vehicle control system is provided with a memory arranged to memorise a last selected control mode that was selected prior to vehicle de-activation or key-off when operating in the automatic control mode selection condition, the system being configured to commence a next journey operating in the memorised control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place.

In a further aspect of the invention for which protection is sought there is provided a motor vehicle control system for selecting and/or determining a driving surface and for controlling a plurality of vehicle subsystems to operate in a plurality of subsystem control modes in dependence on the selected/determined driving surface, the system being operable in a manual control mode selection condition in which a user is able to select said driving surface and an automatic control mode selection condition in which the system is operable to select said driving surface automatically, wherein the vehicle control system is provided with a memory arranged to memorise at the end of a journey a last selected control mode when operating in the automatic control mode selection condition, the system being configured to commence a next journey operating in the memorised control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place.

In a further aspect of the invention for which protection is sought there is provided a motor vehicle control system for selecting and/or determining a driving surface and for controlling a plurality of vehicle subsystems to operate in a plurality of subsystem control modes in dependence on the selected/determined driving surface, the system being operable in a manual control mode selection condition in which a user is able to select said driving surface and an automatic control mode selection condition in which the system is operable to select said driving surface automatically, wherein the vehicle control system is provided with a memory arranged to memorise a last selected control mode that was selected prior to vehicle de-activation or key-off when operating in the automatic control mode selection condition, the system being configured wherein if the next journey is commenced in the automatic control mode selection condition, the system is configured to commence operating in the memorised control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place.

In a further aspect of the invention for which protection is sought there is provided a motor vehicle control system for selecting and/or determining a driving surface and for controlling a plurality of vehicle subsystems to operate in a plurality of subsystem control modes in dependence on the selected/determined driving surface, the system being operable in a manual control mode selection condition in which a user is able to select said driving surface and an automatic control mode selection condition in which the system is operable to select said driving surface automatically, wherein the vehicle control system is provided with a memory arranged to memorise a last selected control mode that was selected prior to vehicle de-activation or key-off when operating in the automatic control mode selection condition, and upon the next subsequent vehicle activation or key-on, the system is configured to continue operating in the memorised control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place.

It is to be understood that a control mode may also be referred to as an operating mode.

It is to be understood that by key-on is meant a transition of a vehicle from a condition in which starting of a prime mover such as an engine or electric machine may not proceed due to the absence of an operation performed by a key or key-fob to a condition in which starting of the prime mover may proceed due to an operation performed by the key or key-fob. For example in the case of a conventional key-twist starting system in an engine-only vehicle, introduction of a key into a key-slot and turning of the key to a prescribed position such as an ‘ON’ position (known as ‘switching on’) may be considered to be key-on, since further turning may result in activation of a starter motor to start an engine. The key serves the dual purpose of placing the vehicle in a condition ready to start by turning to the ‘start’ position, and then activation of a starter motor by momentarily rotating the key through a further partial turn. The ‘ON’ position may correspond to an ‘ignition on’ condition in engines requiring spark ignition such as petrol engines, whilst the ‘ON’ position may correspond to a ‘fuel on’ position in engines relying on compression-ignition, such as diesel engines.

In some embodiments turning of the key to an ‘ON’ position must be followed by depression of a start button before the engine is started rather than further rotation of a key.

In some embodiments key-on takes place when a vehicle detects the presence of a remote key-fob. In some embodiments the remote fob may comprise a radio frequency identification (RFID) device that may be detected by an RFID receiver fitted to a vehicle. When the receiver detects the presence of the key-fob the vehicle assumes a key-on condition in which the control system begins to perform operations associated with driving of the vehicle that are not performed in the key-off condition, typically so as to reduce power consumption. In some embodiments a ‘start’ button or other button must be pressed before a driving mode of a transmission may be selected or a prime mover such as an engine or electric machine started.

Vehicle activation may be considered to take place in some embodiments when an engine is started, or when an automatic transmission is caused to assume a driving mode such as REVERSE, DRIVE, SPORT or other driving mode in which the transmission allows torque to be transmitted from a transmission input shaft or portion to a transmission output shaft or portion.

In some embodiments, by activation is included starting of an engine, for example by pressing a start button, or depressing an accelerator or throttle pedal. In some embodiments starting of the engine may be accomplished in an ‘all electric’ manner without a user being required to press a button or insert a key into a slot. In the case of an electric or hybrid electric vehicle having an automatic transmission, following detection of the presence of a key-fob at key-on, the control system may be operable to cause an electric propulsion motor to accelerate the vehicle from rest when a transmission is placed in a driving mode and an accelerator pedal is pressed without an intermediate step of pressing a start button. In some embodiments a start button must be pressed before the transmission may be moved into a driving mode and the vehicle moved.

Key-off may be considered to take place when a vehicle is shut down. This may be a consequence of the key-fob no longer being within a required range of the vehicle 100. Alternatively or in addition, key-off may take place when a vehicle is locked following exiting of occupants. It is to be understood that a control system may continue operating for a period of time following key-off. However because the key-off condition has been assumed, starting of the vehicle is not permitted due to the absence of the key-fob.

Similarly, vehicle deactivation may be considered to take place in some embodiments when the PARK or NEUTRAL modes of the transmission are assumed. Other means for vehicle activation and deactivation are also useful.

Optionally, when operating in the automatic control mode selection condition, the system is configured to select the most appropriate subsystem control mode by:

(1) for each type of control mode, calculating the probability that the control mode is suitable for the terrain or driving surface over which the vehicle is travelling, based on a plurality of terrain indicators, the terrain indicators being determined according to the value of one or more vehicle operating parameters; (2) integrating positive differences between the probability for the current control mode and that for each of the other control modes; and (3) when the integrated value of the positive differences between the current control mode and one of the other control modes exceeds a pre-determined threshold, assuming that control mode.

It is to be understood that negative differences between control modes are ignored. That is, negative differences are not added whilst the integrated value is being calculated.

It is to be understood that the integrated values of the positive differences may be stored by the control system in a temporary memory thereof as the integration process proceeds.

Optionally, prior to commencement of a journey, for example at vehicle activation or key-on the system is configured to set the integrated value of the positive differences for each control mode to a prescribed value.

That is, the integrated value of the positive differences for each control mode does not remain at the same value following vehicle activation or key-on as when a vehicle terminates motion over a surface, and vehicle deactivation or key-off takes place. Rather, the values are set to respective prescribed values that are pre-stored by the control system. The values may be dependent on the control mode in which the vehicle was operating when motion over the surface terminated and vehicle deactivation or key-off took place. The use of pre-stored values has the advantage that the values may be chosen so as to decrease a likelihood that the vehicle changes control mode soon after motion of the vehicle over the surface resumes.

Optionally, the prescribed value is substantially zero.

By substantially zero is meant that the values are equal to or close to a minimum value of a range of possible values of the integrated values, optionally to within 10%, optionally to within 1% of the minimum value.

Optionally, the Integrated value for each control mode is set to a respective prescribed value prior to commencement of a journey, for example at vehicle activation, key-on, 0.

Thus the integrated value for each mode may be set to a respective prescribed value for that mode.

In some embodiments, this has the advantage that the system must capture more data as the vehicle moves before it is able to change selected operating mode with confidence. It is to be understood that if the values were not reset to a prescribed value such as zero, and at vehicle deactivation or key-off the values were such that the integrated value of the positive difference between the probability that the current mode is the correct mode and the probability that a different mode is the correct mode is almost at the threshold for change, the threshold may be exceeded very soon after the vehicle resumes motion, triggering a change. Embodiments of the present invention have the advantage that a risk that the threshold is exceeded too soon after the vehicle begins moving may be reduced.

Optionally, the system may be configured to set at least one of the plurality of terrain indicators to a prescribed value after the end of a journey and prior to commencement of a new journey, for example at key-off, vehicle deactivation, key-on or vehicle activation.

It is to be understood that the terrain indicators may be set such that, when a vehicle commences motion over a surface, the system employs a prescribed value of at least one of the plurality of terrain indicators when calculating the most appropriate control mode.

Optionally, the prescribed value is a value that is at or close to a middle of a range of values allowed for that parameter.

Optionally, the prescribed value is a value that is at or close to a middle of a range of values allowed for that parameter before a threshold for change of control mode is triggered.

Optionally, the at least one terrain indicator includes a value of surface coefficient of friction between a wheel and a driving surface.

Optionally, the system may be configured to set the value of surface coefficient of friction to a value of substantially 0.5 at key-off, vehicle deactivation, key-on or vehicle activation.

Alternatively, the value of surface coefficient of friction may be any other suitable value. It is to be understood that the prescribed value of the one or more terrain indicators may be state specific prescribed parameter values such as a surface coefficient of friction between a tyre and driving surface, ambient temperature or any other suitable state parameter.

Some embodiments of the invention have the feature that a journey may be commenced with the parameters substantially in the middle of a state estimator band. For example, if when a vehicle shuts down (at key-off) or at deactivation it is in GGS mode, when it starts up again (at key-on) or at activation, the value of surface coefficient of friction, mu, which may be considered to vary from zero to one for the case of a conventional tyre on a driving surface, will not be assumed to be 1, as might normally be the case. Instead it will be assumed to be (say) 0.5 so that the system remains in the GGS mode for a longer period of time. As the vehicle moves over ground the control system will detect prevailing conditions and refine its estimate of the value(s) of the one or more parameters indicative of terrain type (terrain indicators) accordingly. This has the advantage that the system must capture more data obtained as the vehicle moves before it is able to change selected operating mode with confidence. Initial values may be held or reset based on the most effective set-up for start-up.

Optionally, the system may be arranged to memorise the last selected control mode after the end of a journey, for example in response to key-off or vehicle deactivation.

Thus, the system may memorise the last selected control mode when key-off or vehicle deactivation is performed.

Optionally, the system may memorise the last selected control mode prior to vehicle key-off or deactivation by memorising the last selected control mode when a signal indicative that a vehicle may remain at the same location for a period of time exceeding a prescribed period is received.

Optionally, memorising the last selected control mode prior to vehicle deactivation includes memorising the last selected control mode when a transmission of the vehicle is placed into a PARK or NEUTRAL mode.

Thus the system may be configured to receive a signal indicative that a transmission is in a PARK or NEUTRAL mode. Placing the transmission in a PARK or NEUTRAL mode from a driving mode such as REVERSE or DRIVE may be considered to be vehicle deactivation in some embodiments.

In some embodiments the system then resets to a prescribed value the value of one or more parameters such as the value of surface coefficient of friction of a driving surface, a value corresponding to the integral of positive differences between the probability that the current control mode is the most appropriate mode and the probability that each of the other control modes is the most appropriate mode, or any other suitable parameter.

In an embodiment, the control system may take vehicle load variables into account by monitoring seat occupancy, fuel tank contents etc., so as to make more accurate calculations of one or more parameters such as rolling resistance.

Optionally, the system is arranged wherein a transition from PARK or NEUTRAL to a forward drive mode is considered to be a vehicle activation.

Thus if a transition from PARK of NEUTRAL to a forward drive mode such as DRIVE takes place, the system may be configured to continue operating in the same control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place.

Optionally, the system may be arranged to remain in the last selected control mode if a user shifts from a forward gear to a reverse gear.

Optionally, when a user shifts from a forward gear to a reverse gear the system is configured to remain in the last selected control mode until a forward gear is subsequently selected.

This feature reduces the likelihood that a change of control mode takes place whilst the vehicle is reversing, causing a change in handling characteristics whilst performing a reversing manoeuvre.

Optionally, when the forward gear is subsequently selected the system is configured to remain in the last selected control mode until the vehicle has travelled a predetermined distance, or a predetermined time has elapsed.

The predetermined distance may be a distance of around 5 m although other values are also useful. The distance is selected so as to give the system time and data samples to re-determine the type of the prevailing terrain. In some embodiments when the forward gear is selected the system resets to a prescribed value: the value of the one or more parameters such as the value of surface coefficient of friction of a driving surface; a value corresponding to the integral of positive differences between the probability that the current control mode is the most appropriate mode and the probability that each of the other control modes is the most appropriate mode; or any other suitable parameter.

Optionally, the system is arranged after a journey has ended, for example at key off or vehicle deactivation to store data indicative of a last known gear ratio of a range transmission.

The range transmission may be operable at a low range ratio and a high range ratio. The range transmission may be provided by a power transfer unit (or transfer case or power take-off unit) or by means of a separate discrete range transmission that does not serve the function of coupling rear wheels of a vehicle to a torque transmission path from a prime mover such as an engine.

Optionally, if prior to commencement of a journey, for example at key-on or vehicle activation the gear ratio of the range transmission has changed in comparison to the stored data, the system is configured to assume a set of default settings for the vehicle sub-systems.

Optionally, if prior to commencement of a journey, for example at key-on or vehicle activation the gear ratio of the range transmission has changed in comparison to the stored data, the system is configured to assume a prescribed one of the control modes.

The prescribed one of the control modes may be referred to as the default control mode when a gear ratio of the range transmission is detected to have changed at key-on or vehicle activation. The default control mode may be an on-road control mode.

It is to be understood that a change in selected range indicates the vehicle is most likely about to experience a different use case from that which it had been used in prior to key-off or vehicle deactivation. Accordingly, at key-on or vehicle activation the system may be configured not to assume the previously selected control mode, but instead to assume the default control mode.

Optionally, the system is arranged after a journey has ended such as at key off or vehicle deactivation to store data indicative of a last known ride height setting of a suspension system.

Optionally, if prior to commencement of a journey, for example at key-on or vehicle activation the ride height setting of a suspension system is determined to have changed, the system is configured to assume a set of default settings for the vehicle sub-systems.

Optionally, if prior to commencement of a journey, for example at key-on or vehicle activation the ride height setting of a suspension system is determined to have changed, the system is configured to assume a prescribed one of the control modes.

The prescribed one of the control modes may be referred to as a default control mode when a ride height setting of a suspension system is detected to have changed at key-on or vehicle activation. The default control mode may be an on-road control mode.

Thus, in an embodiment, the control system is arranged to store a last known ride height setting. In one embodiment, if the ride-height has changed due to positive manual intervention by a user (for example by commanding a change in ride-height via a user ride height adjustment control) whilst being parked, the control system may be configured to adopt the last known control mode at key-on. Alternatively, in some embodiments the control system may be configured to ignore the last known control mode and employ a set of default sub-system control settings (subsystem configuration modes) instead. This is because a change in ride height typically indicates that the vehicle is about to experience a different use case from that which it had been used in prior to key-off. The default sub-system control settings may correspond to one of the control modes, optionally an on-road control mode.

In an embodiment, the control system may be arranged to store data pertaining to one or more parameters, optionally including environmental parameters such as ambient temperature, rain sensor activity, wading sensor activity, tyre pressure monitoring sensor activity (TPMS) and/or one or more other parameters at key off and/or whenever the vehicle gearbox is set to PARK. If the system determines that values of one or more parameters have changed significantly at key-on or when the gearbox is shifted from PARK to DRIVE or REVERSE or NEUTRAL, the system may be configured to adopt the last known control mode at subsequent key-on. Alternatively the system may ignore the last known control mode and employ a set of default sub-system control settings. The default sub-system control settings may correspond to one of the control modes, optionally an on-road control mode.

It is to be understood that this has the advantage for example that if the temperature falls significantly overnight, the system can adapt to the likelihood of there being snow or ice around the car at key-on even though the ground may have been clear of snow or ice at key-off/deactivation. Monitoring the readings from the TPMS sensors in each wheel may permit the system to identify when a driver has raised or lowered all four tyre pressures together whilst the vehicle was parked, indicative of the driver preparing to operate the vehicle in a different use case or operational situation compared with that which was the case before the vehicle was parked.

Some embodiments of the present invention allow the control system more time to obtain data in respect of prevailing terrain conditions when a vehicle first starts moving before allowing an automatic change in control mode. This increases a confidence with which the system may command automatically a change in selected control mode when it is determined that a change in control mode is required.

Embodiments of the present invention help to ensure that operation of the system in respect of the performance of automatic mode changes is as imperceptible as possible to a user. Embodiments of the invention have the advantage of reducing the chance that unnecessary control mode changes take place at the beginning of a journey.

Optionally, the control modes are control modes of at least one subsystem of a vehicle, the system comprising a subsystem controller for initiating control of the or each of the vehicle subsystems in the selected one of the plurality of subsystem control modes, each of which subsystem control modes corresponds to one or more different driving surfaces.

Optionally, when in the automatic condition the system is operable automatically to control the subsystem controller to initiate control of the or each subsystem in the selected control mode.

Optionally, the control modes are control modes of at least one vehicle subsystem selected from amongst an engine management system, a transmission system, a steering system, a brakes system and a suspension system.

Optionally, the control modes are control modes of at least two vehicle subsystems selected from amongst an engine management system, a transmission system, a steering system, a brakes system and a suspension system.

The control modes may be control modes of each of these systems.

Optionally, in each system operating mode the system is operable to cause each one of a plurality of vehicle subsystems to be operated in a subsystem configuration mode appropriate to the driving surface.

For example, in the case of a vehicle sub-system in the form of a suspension system operable at a plurality of different ride-heights for a given vehicle loading, the subsystem configuration modes may include modes corresponding to different respective ride heights. In the case of a vehicle sub-system controller in the form of an engine or powertrain controller, the controller may be operable to provide different respective values of engine torque as a function of accelerator pedal position in each of a plurality of different powertrain controller configuration modes. A subsystem control mode may therefore correspond to a set of subsystem configuration modes, for example one configuration mode for each subsystem. For example in one control mode a ‘high’ ride height subsystem configuration mode (as opposed to a ‘low’ ride height subsystem configuration mode) may be set for the suspension system and a ‘slow’ accelerator pedal map subsystem configuration mode (as opposed to a ‘quick’ subsystem configuration mode) may be set for the powertrain controller. Some subsystems may allow two different parameters to be set. Thus the suspension system may allow a roll stiffness setting of the suspension to be set to one of a plurality of configuration modes such as low, medium or high stiffness, in addition to a ride height setting.

Various possible known subsystem configuration modes will now be described. The reader is referred to US2003/0200016 for further details in respect of known types of subsystem configuration mode and the manner in which the configuration modes may be implemented. Other configuration modes are also useful. Other subsystems may also be controlled, in addition or instead.

Optionally, the control modes include control modes of a suspension system and the plurality of subsystem configuration modes comprise a plurality of ride heights.

The suspension system may be a fluid suspension system. The fluid employed by the suspension system may be a gas such as air. The fluid may be a liquid in some alliterative embodiments.

Optionally, the control modes include control modes of a fluid suspension system in which fluid interconnection can be made between suspensions for wheels on opposite sides of the vehicle, and wherein said plurality of subsystem configuration modes provide different levels of said interconnection.

Optionally, the control modes include control modes of a steering system which can provide steering assistance, and wherein said plurality of subsystem configuration modes provide different levels of said steering assistance.

Optionally, the control modes include control modes of a brakes system which can provide braking assistance, and said plurality of subsystem configuration modes provide different levels of said braking assistance.

Optionally, the control modes include control modes of a brake control system which can provide an anti-lock function to control wheel slip, and said plurality of subsystem configuration modes allow different levels of said wheel slip.

Optionally, the control modes include control modes of a traction control system which is arranged to control wheel spin, and said plurality of subsystem configuration modes allow different levels of said wheel spin.

Optionally, the control modes include control modes of a yaw control system which is arranged to control vehicle yaw, and said plurality of subsystem configuration modes allow different levels of divergence of said vehicle yaw from an expected yaw.

Optionally, the control modes include control modes of a range change transmission and said subsystem configuration modes may include a high range mode and a low range mode of said transmission.

As noted above, the range change transmission may for example by comprised by a power transfer unit or power take-off unit for coupling a prop shaft of a driveline to a torque transmission path from an engine or transmission of the vehicle, such as an automatic transmission.

Optionally, the control modes include control modes of a powertrain system which includes a powertrain control means and an accelerator or throttle pedal, the subsystem configuration modes providing different levels of responsiveness of the powertrain control means to movement of the accelerator or throttle pedal.

Optionally, the control modes include control modes of a transmission system operable in a plurality of transmission ratios and including a transmission control means (such as an electronic transmission controller) arranged to monitor at least one parameter of the vehicle and to select the transmission ratios in response, and wherein the subsystem configuration modes include a plurality of transmission configuration modes in which the transmission ratios are selected differently in response to said at least one parameter.

One of the subsystems may comprise a differential system operable to provide a plurality of levels of differential lock, and the subsystem configuration modes may be arranged to provide different levels of said lock.

The differential system may be arranged to control the level of differential lock on the basis of a plurality of inputs, and to respond differently to said inputs in each of the modes.

The differential system may comprise a centre differential, a front differential, and/or a rear differential. The differential may be a clutch-based system in some embodiments, whereby differences in rates of rotation of wheels is accommodated by slipping of a clutch rather than by means of a conventional differential gear arrangement in which side wheels are coupled via pinion wheels supported by a differential cage in order to allow relative rotation.

One of the subsystems may comprise a vehicle body roll control system arranged to provide body roll correction to reduce vehicle body roll and the subsystem configuration modes provide different levels of body roll correction of the vehicle, at least under some driving conditions.

One of the subsystems may comprise a speed control system arranged to control the speed of the vehicle when descending a hill. The speed control system may be arranged to control the vehicle to different speeds in the different configuration modes. The speed control system may be a hill descent control (HDC) system.

Optionally, the control modes may include an off-road mode in which the subsystems are controlled in a manner suitable for driving on rough terrain and an on-road mode in which the subsystems are controlled in a manner suitable for driving on-road.

Optionally the suspension system is arranged to provide a higher ride height in the off road mode than in the on-road mode.

Further optionally, in the off-road mode a higher level of said interconnection is provided than in the on-road mode.

The traction control system may be arranged to allow less wheel spin in the off-road mode than in the on-road mode. Alternatively the traction control system may be arranged to allow more wheel spin in the off-road mode than in the on-road mode.

Optionally the yaw control system is arranged to allow a higher degree of said divergence in the off-road mode than in the on-road mode.

Optionally, in the off-road mode the range change transmission is operated in the low range.

Optionally, in the off-road mode the powertrain control means is arranged to provide lower levels of drive torque, for a given accelerator or throttle pedal position, at least at low levels of accelerator pedal depression, than in the on-road mode.

Optionally, the differential system is arranged to provide higher levels of differential lock in the off-road mode than in the on-road mode.

Optionally, the roll control system is arranged to provide a higher roll stiffness in the on-road mode than in the off-road mode.

Optionally, the speed control system is arranged to be switched on in the off-road mode and switched off in the on-road mode.

Optionally, the driving modes include at least one low friction mode in which the subsystems are controlled in a manner suitable for driving on low friction surfaces and a high friction mode in which the subsystems are controlled in a manner suitable for driving on high friction surfaces.

Optionally, the brake control system allows higher levels of slip in the high friction mode than in the low friction mode.

Optionally, the traction control system allows higher levels of wheel spin in the high friction mode than in the low friction mode.

Optionally, the braking control system provides a greater level of braking assistance in the high friction mode than in the low friction mode.

Optionally, the powertrain control means is arranged to provide lower levels of drive torque, for a given accelerator or throttle pedal position, at least at low levels of accelerator pedal depression, in the low friction mode than in the high friction mode.

Optionally, the transmission system is arranged to operate in higher gears for a given value of said at least one parameter in the high friction mode than in the low friction mode.

Optionally, the differential system is arranged to provide higher levels of differential lock in the low friction mode than in the high friction mode.

Optionally, the high friction mode may comprise a standard or default mode in which the vehicle will operate normally and which is suitable for on-road driving.

Optionally, there are at least two such low friction modes and the suspension system is arranged to provide a higher ride height in one of the low friction modes than in the other.

Further optionally, there are at least two such low friction modes and the suspension system is arranged to provide a higher level of said cross linking in one of the low friction modes than in the other.

Optionally, the at least two low friction modes may comprise a mud mode suitable for traveling through deep mud, and another low friction mode suitable for driving in snow, on grass, or on gravel.

Optionally there may be a plurality of low friction modes, one of which may be a grass mode in which the subsystems are controlled in a manner suitable for driving on grass, one of which may be an ice mode in which the subsystems are controlled in a manner suitable for driving in ice, and one of which may be a mud mode in which the subsystems are controlled in a manner suitable for driving on mud.

Optionally one of the modes is a sand mode in which the subsystems are controlled in a manner suitable for driving on sand. At least one of the subsystems may be arranged, in the sand mode, to allow only relatively low levels of wheel spin when the vehicle is traveling at low speeds so as to avoid the vehicle wheels becoming submerged in sand, but to allow relatively high levels of wheel spin when the vehicle is traveling at higher speeds. Optionally, in the sand mode, the powertrain control system is arranged to provide relatively low levels of drive torque for a given throttle pedal position at low vehicle speeds and to provide relatively high levels of drive torque for a given throttle pedal position at higher vehicle speeds.

The off-road mode may be a rock crawl mode in which the subsystems are controlled in a manner suitable for driving over rocks. Alternatively it may be set up for more general off-road use. One or more other off-road modes may be provided in addition or instead.

One of the modes may be a rough-road mode in which the subsystems are controlled in a manner suitable for driving on rough roads, for example for driving at relatively high speeds over rough surfaces.

At least one of the modes may be a plough surface mode in which the brake control subsystem is arranged to allow a relatively high degree of wheel slip under braking. This may be useful, for example on snow or sand, where the build-up of matter in front of the wheels under braking can improve braking performance.

Optionally, at least one of the modes is an on-road mode in which the subsystems are controlled in a manner suitable for driving on-road. For example, one of the modes may be a motorway mode in which the subsystems are controlled in a manner suitable for driving at high speed on a flat road surface. One of the modes may be a country road mode in which the subsystems are controlled in a manner suitable for driving on country roads.

The driving modes may be selectable by means of at least two inputs, one of which may be a terrain selection input arranged to influence the mode selected on the basis of the terrain selected, and the other of which may be a mode of use input arranged to influence the mode selected on the basis of a selected mode of use of the vehicle. Each of these inputs may be user-controlled inputs, or may be derived from one or more sensors.

The mode of use input may be arranged to allow selection between a plurality of driving styles, which may include, for example, a normal style, a sport style, and an economy style.

Alternatively, or in addition, the mode of use input may be arranged to allow selection between a plurality of states of the vehicle, for example including a towing state or a loaded state.

Optionally, the system is operable to select a control mode in which the vehicle is to operate upon vehicle activation or key-on in dependence at least in part on an amount of time that has elapsed since vehicle deactivation or key-off.

The elapsed time may be arranged to be one of that between key-off and key-on, or between vehicle deactivation and activation, or between key-off and vehicle activation, or between vehicle deactivation and key-on. Other arrangements are also useful, and included within the scope of the present claims.

Optionally, if the amount of elapsed time exceeds a first prescribed value the system is configured to assume a first prescribed control mode upon vehicle activation or key-on.

The first prescribed value of time may be any suitable value such as 5 hours, 6 hours, 10 hours or any other suitable value.

Optionally, the first prescribed control mode is determined in dependence at least in part on the control mode in which the vehicle last operated at the end of a journey, for example at key-off or vehicle deactivation.

Optionally, the first prescribed control mode is an on-road control mode.

The control mode may be a special programs off (SPO) control mode suitable for travel on-road.

Optionally, if the amount of time exceeds a second prescribed value greater than the first, the system is configured to assume a second prescribed control mode different from the first.

Thus a tiered choice of control mode may be made, in dependence on the amount of time elapsed since key off. The choice of first, second and any further control modes may be made taking into account that the longer the time that elapses, the greater the likelihood of a change in driving surface, for example due to precipitation, a change in temperature or any other factor or parameter influencing the driving surface. Accordingly the first, second and any further control modes may be selected so as to tend towards a control mode corresponding to driving on-road.

The system may be configured to continue operating in the memorised control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place by suspending changes in operating mode following commencement of movement of a vehicle over a surface when the system is in the automatic operating mode selection condition. Changes may be suspended for a prescribed period of time since movement was commenced. Alternatively or in addition, changes may be suspended for a prescribed distance of travel.

In a further aspect of the invention for which protection is sought there is provided a method of controlling a motor vehicle implemented by a control system, the method comprising selecting and/or determining a driving surface and controlling a plurality of vehicle subsystems to operate in a plurality of subsystem control modes in dependence on the selected/determined driving surface,

whereby in a manual control mode selection condition, selecting and/or determining the driving surface comprises selecting and/or determining the driving surface by reference to a user input in respect of the driving surface; and

-   -   in an automatic control mode selection condition, selecting         and/or determining the driving surface comprises selecting said         driving surface automatically,         wherein the method comprises storing in a memory of the system a         last selected control mode that was selected prior to vehicle         de-activation or key-off, and upon the next subsequent vehicle         activation or key-on, continuing to operate in the same control         mode and to automatically obtain new data in respect of a         driving surface over which the vehicle is moving before allowing         a change in control mode to take place.

A method of controlling a motor vehicle implemented by a control system, the method comprising selecting and/or determining a driving surface and controlling a plurality of vehicle subsystems to operate in a plurality of subsystem control modes in dependence on the selected/determined driving surface,

-   -   whereby in a manual control mode selection condition, selecting         and/or determining the driving surface comprises selecting         and/or determining the driving surface by reference to a user         input in respect of the driving surface; and     -   in an automatic control mode selection condition, selecting         and/or determining the driving surface comprises selecting said         driving surface automatically,     -   wherein the method comprises storing in a memory of the system         at the end of a journey a last selected control mode, and         continuing to operate in the same control mode at a start of the         next journey and to automatically obtain new data in respect of         a driving surface over which the vehicle is moving before         allowing a change in control mode to take place.

In one aspect of the invention for which protection is sought there is provided a carrier medium carrying computer readable code for controlling a vehicle to carry out a method according to an aspect of the invention.

Within the scope of this application it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

For the avoidance of doubt, it is to be understood that features described with respect to one aspect of the invention may be included within any other aspect of the invention, alone or in appropriate combination with one or more other features.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures in which:

FIG. 1 is a schematic illustration of a vehicle according to an embodiment of the present invention;

FIG. 2 is a block diagram to illustrate a vehicle control system in accordance with an embodiment of the invention, including various vehicle subsystems under the control of the vehicle control system;

FIG. 3 is a table showing which vehicle subsystem configuration mode is selected in each respective vehicle operating mode;

FIG. 4 is a schematic illustration of a switchpack according to an embodiment of the invention with a rotary knob in a deployed condition;

FIG. 5 is a schematic illustration of a switchpack according to an embodiment of the invention with a rotary knob in a retracted condition;

FIG. 6 is a schematic illustration of a vehicle according to an embodiment of the present invention towing a trailer; and

FIG. 7 is a flow diagram illustrating a method of operation of a vehicle according to an embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a vehicle 100 according to an embodiment of the invention intended to be suitable for off-road use, that is for use on terrains other than regular tarmac road, as well as on-road. The vehicle 100 has a powertrain 129 that includes an engine 121 that is connected to a driveline 130 having a transmission 124. In the embodiment shown the transmission 124 is an automatic transmission 124. Embodiments of the present invention are also suitable for use in vehicles with a manual transmission, continuously variable transmission or any other suitable transmission.

The driveline 130 is arranged to drive a pair of front vehicle wheels 111, 112 by means of a front differential 135F and a pair of front drive shafts 118. The driveline 130 also comprises an auxiliary driveline portion 131 arranged to drive a pair of rear wheels 114, 115 by means of an auxiliary driveshaft or prop-shaft 132, a rear differential 135 and a pair of rear driveshafts 139. Embodiments of the invention are suitable for use with vehicles in which the transmission is arranged to drive only a pair of front wheels or only a pair of rear wheels (i.e. front wheel drive vehicles or rear wheel drive vehicles) or selectable two wheel drive/four wheel drive vehicles. In the embodiment of FIG. 1 the transmission 124 is releasably connectable to the auxiliary driveline portion 131 by means of a power transfer unit (PTU) 137, allowing selectable two wheel drive or four wheel drive operation. It is to be understood that embodiments of the invention may be suitable for vehicles having more than four wheels or where only two wheels are driven, for example two wheels of a three wheeled vehicle or four wheeled vehicle or a vehicle with more than four wheels.

The PTU 137 is operable in a ‘high ratio’ or a ‘low ratio’ configuration, in which a gear ratio between an input shaft and an output shaft thereof is selected to be a high or low ratio. The high ratio configuration is suitable for general on-road or ‘on-highway’ operations whilst the low ratio configuration is more suitable for negotiating certain off-road terrain conditions and other low speed applications such as towing.

The vehicle 100 has an accelerator pedal 161, brake pedal 163 and steering wheel 181. The steering wheel 181 has a cruise control selector button 181C mounted thereto for activating a cruise control system 11.

The vehicle 100 has a central controller, referred to as a vehicle control unit (VCU) 10. The VCU 10 receives and outputs a plurality of signals to and from various sensors and subsystems 12 provided on the vehicle 100.

FIG. 2 shows the VCU 10 in more detail. The VCU 10 controls a plurality of vehicle subsystems 12 including, but not limited to, an engine management system 12 a, a transmission system 12 b, an electronic power assisted steering unit 12 c (ePAS unit), a brakes system 12 d and a suspension system 12 e. Although five subsystems are illustrated as being under the control of the VCU 10, in practice a greater number of vehicle subsystems may be included on the vehicle and may be under the control of the VCU 10. The VCU 10 includes a subsystem control module 14 which provides control signals via line 13 to each of the vehicle subsystems 12 to initiate control of the subsystems in a manner appropriate to the driving condition, such as the terrain, in which the vehicle is travelling (referred to as the terrain condition). The subsystems 12 also communicate with the subsystems control module 14 via signal line 13 to feedback information on subsystem status. In some embodiments, instead of an ePAS unit 12 c, a hydraulically operated power steering unit may be provided.

The VCU 10 receives a plurality of signals, represented generally at 16 and 17, which are received from a plurality of vehicle sensors and are representative of a variety of different parameters associated with vehicle motion and status. As described in further detail below, the signals 16, 17 provide, or are used to calculate, a plurality of driving condition indicators (also referred to as terrain indicators) which are indicative of the nature of the condition in which the vehicle is travelling. One advantageous feature of some embodiments of the present invention is that the VCU 10 determines the most appropriate control mode for the various subsystems on the basis of the terrain indicators, and automatically controls the subsystems accordingly. That is, the VCU 10 determines the most appropriate control mode on the basis of the terrain indicators and automatically causes each of the subsystems 12 to operate in the respective subsystem configuration mode corresponding to that control mode.

The sensors (not shown) on the vehicle include, but are not limited to, sensors which provide continuous sensor outputs 16 to the VCU 10, including wheel speed sensors, an ambient temperature sensor, an atmospheric pressure sensor, tyre pressure sensors, yaw sensors to detect yaw, roll and pitch of the vehicle, a vehicle speed sensor, a longitudinal acceleration sensor, an engine torque sensor (or engine torque estimator), a steering angle sensor, a steering wheel speed sensor, a gradient sensor (or gradient estimator), a lateral acceleration sensor (part of a stability control system (SCS)), a brake pedal position sensor, an acceleration pedal position sensor and longitudinal, lateral, vertical motion sensors.

In other embodiments, only a selection of the aforementioned sensors may be used. The VCU 10 also receives a signal from the electronic power assisted steering unit (ePAS unit 12 c) of the vehicle to indicate the steering force that is applied to the wheels (steering force applied by the driver combined with steering force applied by the ePAS unit 12 c).

The vehicle 100 is also provided with a plurality of sensors which provide discrete sensor output signals 17 to the VCU 10, including a cruise control status signal (ON/OFF), a transfer box or PTU 137 status signal (whether the gear ratio is set to a HI range or a LO range), a Hill Descent Control (HDC) status signal (ON/OFF), a trailer connect status signal (ON/OFF), a signal to indicate that the Stability Control System (SCS) has been activated (ON/OFF), a windscreen wiper signal (ON/OFF), an air suspension ride-height status signal (HI/LO), and a Dynamic Stability Control (DSC) signal (ON/OFF).

The VCU 10 includes an evaluation means in the form of an estimator module or processor 18 and a calculation and selection means in the form of a selector module or processor 20. Initially the continuous outputs 16 from the sensors are provided to the estimator module 18 whereas the discrete signals 17 are provided to the selector module 20.

Within a first stage of the estimator module 18, various ones of the sensor outputs 16 are used to derive a number of terrain indicators. In a first stage of the estimator module 18, a vehicle speed is derived from the wheel speed sensors, wheel acceleration is derived from the wheel speed sensors, the longitudinal force on the wheels is derived from the vehicle longitudinal acceleration sensor, and the torque at which wheel slip occurs (if wheel slip occurs) is derived from the motion sensors arranged to detect yaw, pitch and roll. Other calculations performed within the first stage of the estimator module 18 include the wheel inertia torque (the torque associated with accelerating or decelerating the rotating wheels). “continuity of progress” (the assessment of whether the vehicle is starting and stopping, for example as may be the case when the vehicle is travelling over rocky terrain), aerodynamic drag, yaw rate, and lateral vehicle acceleration.

The estimator module 18 also includes a second stage in which the following terrain indicators are calculated: surface rolling resistance (based on the wheel inertia torque, the longitudinal force on the vehicle, aerodynamic drag, and the longitudinal force on the wheels), the steering force on the steering wheel 181 (based on the lateral acceleration and the output from the steering wheel sensor), the wheel longitudinal slip (based on the longitudinal force on the wheels, the wheel acceleration, SCS activity and a signal indicative of whether wheel slip has occurred), lateral friction (calculated from the measured lateral acceleration and the yaw versus the predicted lateral acceleration and yaw), and corrugation detection (high frequency, low amplitude wheel height excitement indicative of a washboard type surface).

The SCS activity signal is derived from several outputs from an SCS ECU (not shown), which contains the DSC (Dynamic Stability Control) function, the TC (Traction Control) function, ABS and HDC algorithms, indicating DSC activity, TC activity, ABS activity, brake interventions on individual wheels, and engine torque reduction requests from the SCS ECU to the engine. All these indicate a slip event has occurred and the SCS ECU has taken action to control it. The estimator module 18 also uses the outputs from the wheel speed sensors to determine a wheel speed variation and corrugation detection signal.

On the basis of the windscreen wiper signal (ON/OFF), the estimator module 18 also calculates how long the windscreen wipers have been in an ON state (i.e. a rain duration signal).

The VCU 10 also includes a road roughness module 24 for calculating the terrain roughness based on the air suspension sensors (the ride height sensors) and the wheel accelerometers. A terrain indicator signal in the form of a roughness output signal 26 is output from the road roughness module 24.

The estimates for the wheel longitudinal slip and the lateral friction estimation are compared with one another within the estimator module 18 as a plausibility check.

Calculations for wheel speed variation and corrugation output, the surface rolling resistance estimation, the wheel longitudinal slip and the corrugation detection, together with the friction plausibility check, are output from the estimator module 18 and provide terrain indicator output signals 22, indicative of the nature of the terrain in which the vehicle is travelling, for further processing within the VCU 10.

The terrain indicator signals 22 from the estimator module 18 are provided to the selector module 20 for determining which of a plurality of vehicle subsystem control modes (and therefore corresponding subsystem configuration modes) is most appropriate based on the indicators of the type of terrain in which the vehicle is travelling. The most appropriate control mode is determined by analysing the probability that each of the different control modes is appropriate on the basis of the terrain indicator signals 22, 26 from the estimator module 18 and the road roughness module 24.

The vehicle subsystems 12 may be controlled automatically in a given subsystem control mode (in an “automatic mode” or “automatic condition” of operation of the VCU 10) in response to a control output signal 30 from the selector module 20 and without the need for driver input. Alternatively, the vehicle subsystems 12 may be operated in a given subsystem control mode according to a manual user input (in a “manual mode” or “manual condition” of operation of the VCU 10) via a Human Machine Interface (HMI) module 32. Thus the user determines in which subsystem control mode the subsystems will be operated by selection of a required system control mode (operating mode). The HMI module 32 comprises a display screen (not shown) and a user operable switchpack 170 (FIG. 4). The user may select between the manual and automatic modes (or conditions) of operation of the VCU 10 via the switchpack 170. When the VCU 10 is operating in the manual mode or condition, the switchpack 170 also allows the user to select the desired subsystem control mode.

It is to be understood that the subsystem controller 14 may itself control the vehicle subsystems 12 a-12 e directly via the signal line 13, or alternatively each subsystem may be provided with its own associated intermediate controller (not shown in FIG. 1) for providing control of the relevant subsystem 12 a-12 e. In the latter case the subsystem controller 14 may only control the selection of the most appropriate subsystem control mode for the subsystems 12 a-12 e, rather than implementing the actual control steps for the subsystems. The or each intermediate controller may in practice form an integral part of the main subsystem controller 14.

When operating in the automatic mode, the selection of the most appropriate subsystem control mode may be achieved by means of a three phase process:

(1) for each type of control mode, a calculation is performed of the probability that the control mode is suitable for the terrain over which the vehicle is travelling, based on the terrain indicators;

(2) the integration of “positive differences” between the probability for the current control mode and the other control modes; and

(3) the program request to the control module 14 when the integration value exceeds a pre-determined threshold or the current terrain control mode probability is zero.

The specific steps for phases (1), (2) and (3) will now be described in more detail.

In phase (1), the continuous terrain indicator signals in the form of the road surface roughness output 26 and the outputs 22 from the estimator module 18 are provided to the selector module 20. The selector module 20 also receives the discrete terrain indicators 17 directly from various sensors on the vehicle, including the transfer box status signal (whether the gear ratio is set to a HI range or a LO range), the DSC status signal, cruise control status (whether the vehicle's cruise control system 11 is ON or OFF), and trailer connect status (whether or not a trailer is connected to the vehicle). Terrain indicator signals indicative of ambient temperature and atmospheric pressure are also provided to the selector module 20.

The selector module 20 is provided with a probability algorithm 20 a for calculating the most suitable control mode for the vehicle subsystems based on the discrete terrain indicator signals 17 received directly from the sensors and the continuous terrain indicators 22, 26 calculated by the estimator module 18 and the road surface roughness module 24, respectively. That is, the probability algorithm 20 a calculates the most suitable system control mode, which determines the respective subsystem configuration mode in which each subsystem is to be operated, based on the discrete terrain indicator signals 17.

The control modes typically include a grass/gravel/snow control mode (GGS mode) that is suitable for when the vehicle is travelling in grass, gravel or snow terrain, a mud/ruts control mode (MR mode) which is suitable for when the vehicle is travelling in mud and ruts terrain, a rock crawl/boulder mode (RB mode) which is suitable for when the vehicle is travelling in rock or boulder terrain, a sand mode which is suitable for when the vehicle is travelling in sand terrain (or deep soft snow) and a special programs OFF mode (SP OFF mode or SPO mode) which is a suitable compromise mode, or general mode, for all terrain conditions and especially vehicle travel on motorways and regular roadways. Many other control modes are also envisaged including those disclosed in US2003/0200016, the content of which is hereby incorporated by reference.

The different terrain types are grouped according to the friction of the terrain and the roughness of the terrain. For example, it is appropriate to group grass, gravel and snow together as terrains that provide a low friction, smooth surface and it is appropriate to group rock and boulder terrains together as high friction, very high roughness terrains.

FIG. 3 is a table taken from US2003/0200016 showing the particular sub-system configuration modes assumed by the subsystems 12 of the vehicle 100 in the respective different operating modes in which the VCU 10 may operate.

The operating modes are:

(a) A motorway (or highway) mode;

(b) A country road mode;

(c) A city driving (urban) mode;

(d) A towing (on-road) mode;

(e) A dirt track mode;

(f) A snow/ice (on-road) mode;

(g) A GGS mode;

(h) A sand mode;

(i) A rock crawl or boulder crossing mode; and

(j) A mud/ruts mode

With reference to FIG. 3, the configuration of the suspension system 12 e is specified in terms of ride height (high, standard or low) and side/side air interconnection. The suspension system 12 e is a fluid suspension system, in the present embodiment an air suspension system, allowing fluid interconnection between suspensions for wheels on opposite sides of the vehicle in the manner described in US2003/0200016. The plurality of subsystem configuration modes provide different levels of said interconnection, in the present case no interconnection (interconnection closed) and at least partial interconnection (Interconnection open).

The configuration of the ePAS steering unit 12 c may be adjusted to provide different levels of steering assistance, wherein steering wheel 181 is easier to turn the greater the amount of steering assistance. The amount of assistance may be proportion to vehicle speed in some operating modes.

The brakes system 12 d may be arranged to provide relatively high brake force for a given amount of pressure applied to the brake pedal 163 or a relatively low brake force, depending on the operating mode.

The brakes system 12 d may also be arranged to allow different levels of wheel when an anti-lock braking system is active, (relatively low amounts on low friction (“low-mu” surfaces) and relatively large amounts on high friction surfaces).

An electronic traction control (ETC) system may be operated in a high mu or low mu configuration, the system tolerating greater wheel slip in the low mu configuration before intervening in vehicle control compared with a high mu configuration.

A dynamic stability control system (DSC) may also be operated in a high mu or low mu configuration.

The engine management system 12 a may be operated in ‘quick’ or ‘slow’ accelerator (or throttle) pedal progression configuration modes in which an increase in engine torque as a function of accelerator pedal progression is relatively quick or slow, respectively. The rate may be dependent on speed in one or more modes such as Sand mode.

The PTU 137 may be operated in a high range (HI) subsystem configuration mode or low range (LO) subsystem configuration mode as described herein.

The transmission 124 may be operated in a “normal” mode that provides a reasonable compromise between fuel economy and driving performance, a “performance” mode which generally keeps the transmission in lower gears than in the normal mode, particularly when the driver is requesting a high level of driving torque to accelerate the vehicle, and a “manual” mode in which the control of gear changes is given completely to the driver. There is also a “snow” or “ice” mode which generally keeps the transmission in higher gears than the normal mode, in particular under acceleration from rest, to avoid loss of traction due to wheel spin, and a “sand” mode which keeps the transmission in relatively high gears at low speed to avoid excessive wheel spin. Excessive wheel spin can result in the wheels digging themselves into the sand at low speeds. However, the sand mode uses relatively low gears at higher speeds where a relatively high degree of wheel slip can be desirable to provide maximum traction. Lower gearing also helps the engine 121 to remain in an operating region where the engine speed is high and the power output is high, thereby helping to avoid the vehicle 100 becoming “bogged down” by a lack of power.

In some embodiments, a centre differential and a rear differential each include a clutch pack and are controllable to vary the degree of locking between a “fully open” and a “fully locked” state. The actual degree of locking at any one time may be controlled on the basis of a number of factors in a known manner, but the control can be adjusted so that the differentials are “more open” or “more locked”. Specifically the pre-load on the clutch pack can be varied which in turn controls the locking torque, i.e. the torque across the differential that will cause the clutch, and hence the differential, to slip. A front differential could also be controlled in the same or similar way.

For each subsystem control mode, the algorithm 20 a within the selector module 20 performs a probability calculation, based on the terrain indicators, to determine a probability that each of the different control modes is appropriate. The selector module 20 includes a tuneable data map which relates the continuous terrain indicators 22, 26 (e.g. vehicle speed, road roughness, steering angle) to a probability that a particular control mode is appropriate. Each probability value typically takes a value of between 0 and 1. So, for example, the vehicle speed calculation may return a probability of 0.7 for the RB mode if the vehicle speed is relatively slow, whereas if the vehicle speed is relatively high the probability for the RB mode will be much lower (e.g. 0.2). This is because it is much less likely that a high vehicle speed is indicative that the vehicle is travelling over a rock or boulder terrain.

In addition, for each subsystem control mode, each of the discrete terrain indicators 17 (e.g. trailer connection status ON/OFF, cruise control status ON/OFF) is also used to calculate an associated probability for each of the control modes, GGS, RB, Sand, MR or SP OFF. So, for example, if cruise control is switched on by the driver of the vehicle, the probability that the SP OFF mode is appropriate is relatively high, whereas the probability that the MR control mode is appropriate will be lower.

For each of the different sub system control modes, a combined probability value, Pb, is calculated based on the individual probabilities for that control mode, as described above, as derived from each of the continuous or discrete terrain indicators 17, 22, 26. In the following equation, for each control mode the individual probability as determined for each terrain indicator is represented by a, b, c, d . . . n. The combined probability value, Pb, for each control mode is then calculated as follows: Pb=(a,b,c,d, . . . n)/((a,b,c,d, . . . n)+(1−a),(1−b),(1−c),(1−d), . . . (1−n))

Any number of individual probabilities may be input to the probability algorithm 20 a and any one probability value input to the probability algorithm may itself be the output of a combinational probability function.

Once the combined probability value for each control mode has been calculated, the subsystem control program corresponding to the control mode with the highest probability is selected within the selector module 20 and an output signal 30 providing an indication of this is provided to the subsystem control module 14. The benefit of using a combined probability function based on multiple terrain indicators is that certain indicators may make a control mode (e.g. GGS or MR) more or less likely when combined together, compared with basing the selection on just a single terrain indicator alone.

A further control signal 31 from the selector module 20 is provided to a control module 34.

In phase (2), an integration process is implemented continually within the selector module 20 to determine whether it is necessary to change from the current control mode to one of the alternative control modes.

The first step of the integration process is to determine whether there is a positive difference between the combined probability value for each of the alternative control modes compared with the combined probability value for the current control mode.

By way of example, assume the current control mode is GGS with a combined probability value of 0.5. If a combined probability value for the sand control mode is 0.7, a positive difference is calculated between the two probabilities (i.e. a positive difference value of 0.2). The positive difference value is integrated with respect to time. If the difference remains positive and the integrated value reaches a predetermined change threshold (referred to as the change threshold), or one of a plurality of predetermined change thresholds, the selector module 20 determines that the current terrain control mode (for GGS) is to be updated to a new, alternative control mode (in this example, the sand control mode). A control output signal 30 is then output from the selector module 20 to the subsystem control module 14 to initiate the sand control mode for the vehicle subsystems.

In phase (3), the probability difference is monitored and if, at any point during the integration process, the probability difference changes from a positive value to a negative value, the integration process is cancelled and reset to zero. Similarly, if the integrated value for one of the other alternative control modes (i.e. other than sand), reaches the predetermined change threshold before the probability result for the sand control mode, the integration process for the sand control mode is cancelled and reset to zero and the other alternative control mode, with a higher probability difference, is selected.

HDC Interaction

As described above, the vehicle 100 has an HMI module 32 comprising a user operable switchpack 170 shown schematically in FIG. 4. The switchpack 170 allows a user to toggle the VCU 10 between the automatic and manual conditions of operation.

The switchpack 170 has a frame 170F supporting switchgear associated with the switchpack 170. The switchpack 170 has a rotary knob 172 connected to a multistable rotary switch (not shown). The knob 172 may be moved between an exposed or deployed position as shown in FIG. 3 and a retracted position as shown in FIG. 5. In the exposed position the knob 172 stands proud of a panel 172P which surrounds the knob 172. Icons 172 a-e are marked in the panel at circumferentially spaced apart locations around the knob 172 over an arc of around 140° in the embodiment shown although other angles and other numbers of modes are also useful. The icons 172 a-e may be illuminated selectively in order to indicate the identity of the control mode in which the subsystems 12 are being operated.

Other switches 171 a, b are also provided in a remaining portion of the panel 172P allowing a driver to activate a hill descent control (HDC) function, via switch 171 a, and select a required gear ratio of the PTU 137 (‘high’ or ‘low’), via switch 171 b.

Further switches 171 c of the switchpack enable the SCS system of the vehicle to be activated or deactivated, a ride height to be adjusted (buttons 171 c′), an ‘eco’ mode (arranged to enhance fuel economy) to be selected and an automatic speed limiter (ASL) function to be selected.

The rotary knob 172 has a substantially cylindrical column portion 174 with its cylinder axis oriented substantially vertically. The knob 172 has an upper panel 175 bearing the word ‘AUTO’. When the knob 172 is in the retracted position an indicator lamp 175L of the panel 175 illuminates, indicating that the VCU 10 has assumed the automatic condition in which the VCU 10 selects automatically an appropriate subsystem control mode.

When the knob 172 is in the exposed position the indicator lamp 175L is extinguished, indicating that the VCU 10 has assumed the manual condition. The knob 172 is moved between the exposed and retracted positions by means of a spring mechanism triggered by pressing on the panel 175. Other arrangements are also useful such as an electrical actuator. In some embodiments a switch is integrated into the knob 172 such that pressing on the panel 175 alone actuates the switch to switch between the automatic and manual conditions. In some embodiments the switch is positioned such that sufficient axial pressure applied to substantially any exposed portion of the knob 172 including rim 172R results in actuation of the switch. The knob 172 may be configured to exercise a relatively small axial translation when the switch is actuated, providing tactile feedback to the user, followed by a relatively large axial translation as the knob 172 moves between the exposed and retracted positions or vice versa.

The knob 172 is configured such that the rim 172R may be grasped by the user and rotated about a cylinder axis of the column portion 174. The switchpack 170 is arranged such that the VCU 10 may determine in which direction the user turns the rim 172R based on a signal output by the switchpack 170. In an example rim 172R is provided with a knurled peripheral surface arranged to facilitate the user grasping the knob 172 with their fingers.

Rotation of the rim 172R is indexed in discrete angular increments of around 10-20° by means of a detent mechanism. This allows tactile feedback to be provided to a user confirming when the knob 172 has been rotated through one of the discrete angular increments. Other angles and other arrangements are also useful. The rim 172R may be rotated by any number of turns in either direction without constraint by the switchpack 170.

In some embodiments, when the VCU 10 is in the manual condition, rotation of the rim 172R by two increments in a clockwise (or anticlockwise) direction causes the VCU 10 to assume the mode corresponding to the icon 172 a-e that is located adjacent the icon corresponding to the currently selected mode in a clockwise (or anticlockwise) direction. If no such icon exists then the VCU 10 takes no action and the currently selected mode remains selected. If the user rotates the knob 172R by only a single increment in a given direction, with no further increment in that direction within a prescribed time period (such as 1 s or any other suitable period), no change in control mode takes place. This feature reduces a risk that a user unintentionally changes the selected mode. It is to be understood that any prescribed number of turns by the incremental amount may be required in order to enable a mode change to take place. Furthermore, any prescribed time period may be set within which the prescribed number of turns by the incremental amount (or in addition, or instead any two consecutive incremental amounts) are to take place. In some embodiments, a user is required to rotate the rim 172R by only a single incremental amount in order to signal a requirement to change mode.

In some embodiments, in addition to or instead of rotating the rim 172R of the knob 172 in order to change control mode when the VCU 10 is in the manual condition, the knob 172 may be configured such that mode changes may be effected by rotation of column 174. In some embodiments the rim 172R may be rotatable whilst the column 174 remains stationary, whilst in some alternative embodiments the rim 172R and column 174 may be arranged to rotate together. They may for example be fixedly coupled or integrally formed in some embodiments.

In some embodiments, the VCU 10 may be configured to allow manual selection of a given control mode following user selection of that mode only once it has determined that the user has finished rotating the rim 172R. The VCU 10 may wait a prescribed period of time after the last incremental rotation has been detected, for example up to around 2 s, before allowing a mode change to take place. In some embodiments the VCU 10 may be arranged to effect a mode change a predetermined time after it has been determined that the user has released their grip from the knob 172.

In some embodiments the VCU 10 may be arranged to verify that one or more prescribed vehicle settings or parameters are appropriate to the mode the user wishes to select before allowing a mode change. For example, the VCU 10 may check one or more selected from amongst selected PTU gear ratio, selected ride height and/or one more other settings. If the settings are not appropriate to the mode the user wishes to select, the VCU 10 may be configured to remain in the current control mode until the settings are determined to be appropriate. In the meantime the VCU 10 may cause the icon of the currently selected mode to remain illuminated. The icon corresponding to that of the mode the user wishes the VCU 10 to assume may be arranged to illuminate intermittently in some embodiments, e.g. by flashing. The user may be informed of the one or more deficiencies in settings identified by the VCU 10. If they are not remedied within a prescribed period of time, or in some embodiments if an attempt to remedy them is not commenced within a prescribed period, the VCU 10 may be configured to operate as if the user had not sought to change mode. That is, information in respect of deficiencies is not displayed any longer, and flashing of the icon corresponding to the proposed mode is terminated.

It is to be understood that when a user activates the automatic condition of the VCU 10 the VCU 10 controls the vehicle subsystems to operate in the most appropriate control mode as determined by the VCU 10. The rotary knob 172 assumes the retracted position and any rotation of the rim 172R by a user does not cause a change in the selected control mode. Rather, it is ignored by the VCU 10.

If whilst the VCU 10 is in the automatic condition the manual condition is activated, the VCU 10 controls the vehicle subsystems automatically to assume the SPO mode, being the mode intended to provide the best compromise in vehicle subsystem adjustment/set-up for normal road and light off-road use. The knob 172 also assumes the exposed position. Icon 172 a, which corresponds to the SPO mode, is illuminated.

If a user wishes to select a mode other than the SPO mode, he or she may grasp the rim 172R and rotate the rim 172R in a clockwise direction to select the appropriate mode. If the rim 172R is rotated by two indexed angular increments and the user waits for 2 s, the VCU 10 assumes the GGS mode. Icon 172 a is no longer illuminated and icon 172 b becomes illuminated. If the rim 172R is rotated by two further angular increments, the vehicle will assume MR mode, icon 172 b will no longer be illuminated and icon 172 c will be illuminated instead, and so forth. As noted above, the number of angular increments may be any suitable number such as 1, 3 or any other suitable number. Any other suitable user wait period may also be employed.

Thus it is to be understood that the angular position of the rim 172R when the automatic condition was last selected is irrelevant to the determination of the control mode the VCU 10 will assume when the manual condition is subsequently selected. Regardless of the control mode that was selected when the knob 172 was last retracted, when the knob 172 is subsequently exposed VCU 10 selects the SPO control mode. Because the rim 172R is freely rotatable without constraint (due to the absence of features constraining rotation such as an end stop to prevent further rotation in a given direction) the actual (absolute) angular position of the rim 172R is irrelevant. It is to be understood that if this feature were not employed and the rim 172R were required to be in a prescribed absolute rotational position in order to select SPO mode, additional (automatic) actuation of the rim 172R by the switchpack 170 would be required when transitioning from the automatic to manual conditions of the VCU 10. For example, if the rim 172R had been set to select RB mode prior to the user selecting the automatic condition of the VCU 10, the switchpack 170 would be required to rotate the rim 172R from the position corresponding to the RB mode to that corresponding to the SPO mode when manual mode were subsequently selected. Additional, potentially complicated failsafe countermeasures would be required.

It is to be understood that in some alternative embodiments, when the automatic condition is deselected and the manual condition is assumed, the VCU 10 may be arranged to remain in the driving mode that was selected automatically by the VCU 10 when in the automatic condition until the user selects a different driving mode by rotation of the rim 172R. Thus, when the manual condition is selected, the icon 172 a-e corresponding to the currently (automatically) selected driving mode remains illuminated. If the VCU 10 is configured such that none of icons 172 a-e are illuminated when the VCU 10 is in the automatic condition then the icon corresponding to the currently selected driving mode is illuminated when the manual condition is assumed.

It is to be understood that other arrangements are also useful.

It is to be understood that when the VCU 10 is operating in the manual condition, the HDC function may be selected by means of switch 171 a. When active, the HDC function limits a rate of progress (i.e. a speed) of the vehicle 100 over ground when descending a slope to a prescribed value by application of a foundation braking system of the vehicle 100. In the vehicle 100 of FIG. 1 the foundation braking system is provided by a friction braking system. In some embodiments the foundation braking system may be provided by a regenerative braking system in addition or instead. HDC functionality is described in UK patents GB2325716, GB2308415, GB2341430, GB82382158 and GB2381597.

It is to be understood that if the vehicle is descending a slope, a user may activate the HDC function by pressing switch 171 a. The VCU 10 then assumes control of the foundation braking system and limits the speed at which the vehicle 100 may descend the slope to a user-prescribed value. If the vehicle speed drops below the user-prescribed value the user may increase the speed by pressing the accelerator pedal 161. If the user wishes to decrease speed below the prescribed value temporarily, for example if the user wishes to stop the vehicle, the user may press the brake pedal 163 to activate the foundation braking system in the expected manner.

The VCU 10 is configured wherein if the VCU 10 is operating in the automatic mode selection condition and the user selects the HDC function, the VCU 10 activates the HDC function but suspends any further automatic changes in selected sub-system control mode. That is, the VCU 10 remains in the presently selected control mode when the HDC function is selected. If the VCU 10 is operating in the automatic condition, the VCU 10 may be operable to automatically initialise HDC in a standby mode, such that its function may be armed and waiting to intervene where required. If HDC intervenes whilst the vehicle is travelling with VCU 10 operating in the automatic condition, a control mode change will not be made during the period for which the HDC function is operating and intervening to maintain composed vehicle progress.

In some embodiments the VCU 10 also suspends determination of the most appropriate control mode for the terrain over which the vehicle 100 is travelling until the HDC function is deselected. This feature may reduce a computational burden placed on the VCU 10 whilst the HDC function is active in some embodiments.

In some alternative embodiments the VCU 10 continues to determine the most appropriate control mode for the terrain over which the vehicle 100 is travelling even whilst the HDC function is active. It is to be understood that the reliability of certain terrain indicators used in determining the terrain over which the vehicle 100 is moving may be reduced during HDC intervention. That is, HDC intervention may give rise to an erroneous determination of the type of terrain over which the vehicle is moving and therefore of the most appropriate control mode. Thus the VCU 10 may wait for a prescribed number of wheel rotations to take place, for a prescribed distance to be travelled or for a prescribed time period to elapse once the HDC intervention has ceased before allowing automatic control mode changes to take place.

In some embodiments the VCU 10 may wait for a prescribed time period to elapse or for a prescribed number of wheel rotations to take place or for a prescribed distance to be travelled over terrain having a gradient below a prescribed value before allowing a change in mode to take place automatically.

In some embodiments, when the HDC intervention has ceased, the VCU 10 is arranged to remain in the selected control mode and delay automatic changing of control mode for a prescribed period of time, optionally a prescribed period of from around 5 s to around 2 minutes before allowing a change in control mode to be made automatically whilst the VCU 10 is in the automatic condition. Other values are also useful.

In some embodiments when the HDC function is deactivated the VCU 10 is arranged to remain in the selected control mode for a prescribed distance of travel, optionally a distance of from around 2 m to around 200 m before allowing a change in control mode to be made automatically whilst the VCU 10 is in the automatic condition.

This delay (in distance or time) has the advantage that when the VCU 10 returns to automated control mode following cessation of HOC intervention, the vehicle response to the user pressing of the brake and/or accelerator pedals 163, 161 will be in line with that anticipated and expected by the user, and consistent with that experienced by the driver prior to HDC intervention.

In some embodiments, when the VCU 10 activates the HOC function an HDC-specific relationship between accelerator pedal position and torque developed by the powertrain is implemented by the VCU 10. Similarly a predetermined relationship between brake pedal pressure and brake torque applied by means of the foundation braking system may be established in addition or instead. These values may be independent of the control mode in which the VCU 10 is operating.

In some alternative embodiments, the form of the response of the powertrain 129 and braking system to accelerator and brake pedal inputs respectively is dependent on the selected control mode and corresponds to that implemented when the VCU 10 is in that control mode and the HDC function is not active. Thus it is to be understood that in such embodiments, the fact that changes in control mode are suspended when the HDC function is active have the advantage that a response of the vehicle to accelerator and brake pedal inputs does not change whilst the HDC function is active, i.e. because the selected control mode is not changed. This reduces a risk that a driver is inconvenienced by a change in vehicle response to accelerator and/or brake pedal control inputs when performing a hill descent operation.

Some embodiments of the present invention have the advantage that vehicle composure may be preserved and in some embodiments or situations composure may be enhanced. Some embodiments have the advantage that user confidence in vehicle operation performance and expected response may be enhanced. Automatic terrain recognition and control mode selection may be made with confidence.

Detected Trailer

In another aspect of the invention for which protection is sought there is provided a control system for a motor vehicle, the system being operable in an automatic mode selection condition in which the system is operable to select automatically an appropriate system operating mode whereby the system assumes operation in said system operating mode,

-   -   wherein when operating in the automatic mode selection condition         the system is operable to prevent selection of a prescribed one         or more operating modes if it is determined that the vehicle is         towing a load.

Advantageously the operating modes are control modes of at least one subsystem of a vehicle, the system comprising a subsystem controller for initiating control of the or each of the vehicle subsystems in the selected one of the plurality of subsystem control modes, each of which corresponds to one or more different driving conditions for the vehicle, the system comprising evaluation means for evaluating one or more driving condition indicators to determine the extent to which each of the subsystem control modes is appropriate, wherein when in the automatic condition the system is operable automatically to control the subsystem controller to initiate control of the or each subsystem in the subsystem control mode which is most appropriate.

In an aspect of the invention for which protection is sought there is provided a motor vehicle control system for selecting a driving surface and for controlling a plurality of vehicle subsystems to operate in a plurality of subsystem configuration modes in dependence on the selected driving surface, the system being operable in a manual operating condition in which a user is able to select said driving surface and an automatic operating condition in which the system is operable to select said driving surface automatically, wherein the system is able to be switched between said manual and automatic operating conditions by means of a user-operable input device,

the system being further operable to prevent selection of one or more of the subsystem configuration modes in dependence on a determination as to whether the vehicle is towing a load.

The system may be operable to determine whether or not the vehicle is towing a load according to an input signal indicating whether the vehicle is towing. Alternatively or in addition the system may be operable to determine whether the vehicle is towing by monitoring one or more vehicle parameters and determining whether a value of one or more parameters and/or a variation in a value of one or more parameters over time is indicative of towing.

It is to be understood that when a vehicle is towing a load, an amount of drag on the vehicle is increased due to the weight of the load towed, and increased air resistance. In some embodiments the control system may monitor drag on the vehicle in order to determine the most appropriate subsystem control mode for vehicle operation.

It is possible that when a trailer is connected the system may falsely determine that the vehicle is travelling over a high drag surface such as sand and select a corresponding subsystem configuration mode. This mode may be inappropriate when towing, for example due to a change in powertrain response to accelerator pedal input that is implemented by the mode. Accordingly, embodiments of the present invention have the advantage that when the vehicle is towing and the system is operating in the automatic selection condition, the system is prevented from selection one or more prescribed subsystem operating modes that may be inappropriate when towing.

It is to be understood that in some embodiments a user may still select such a mode when towing by deselecting the automatic operating condition of the system.

In an embodiment the system is operable to prevent selection of a subsystem configuration mode that increases a responsiveness of a powertrain to an accelerator control input. In some embodiments having a subsystem control mode optimised for travel over sand the system may be operable to prevent selection of that mode.

Advantageously, if the system is operating in the automatic selection condition and it is determined that the vehicle is towing, the system is configured automatically to assume the manual selection condition. The system may notify a user that the operating condition has changed, for example by providing a corresponding warning via a display panel such as an HMI display.

In some embodiments, the system may rely on detection of an electrical connection between a trailer and the vehicle in order confidently to determine that the vehicle is towing.

It is to be understood however that such electrical connections are prone to damage. Furthermore, it is known that some users may choose to mechanically hitch a trailer without making an electrical connection if they wish to move a vehicle on private land, or if the electrical connections on the trailer do not match those of the vehicle.

Accordingly, in some embodiments in addition or instead the system may monitor changes in vehicle rolling resistance and/or drag in order to detect coupling of a trailer to the vehicle.

For example if an increase in drag by more than a prescribed threshold is detected immediately following starting of the vehicle from rest after the vehicle has been stationary for longer than a prescribed period, the system may determine that a trailer has been coupled to the vehicle. In some embodiments the system may check for one or more other indicators that the vehicle is towing and not driving on sand before determining that a trailer has been coupled. The system may check seat occupancy data and/or door opening history as described below.

In some embodiments the system may employ data from one or more front or rear mounted parking sensors such as park distance control (PDC) sensors. It is to be understood that when a vehicle is in motion and towing, it is expected that the sensors will detect an object following the vehicle a constant distance from the vehicle, and typically within 2 m of the vehicle. In addition, left-hand and right-hand outboard sensors are expected to detect complimentary changes in distance to the object due to cornering. For example if a distance from a left hand sensor to the object decreases by distance X, a corresponding increase in distance to the object would be expected in respect of the right-hand sensor. Such a change would be indicative of cornering to the left. Correspondingly opposite changes would be expected in respect of cornering to the right.

In some embodiments the system is configured to analyse road roughness data obtained by monitoring front and rear wheel suspension articulation when travelling in a substantially straight line and determine whether one or more characteristics or trends are present in the data indicative of towing. In an example, if the vehicle is towing a trailer, articulation of a rear suspension whilst towing is likely to be influenced by the increased vertical loading at the tow hitch due to the presence of the trailer, which may be around 150 kg in some embodiments.

In order to increase a likelihood that the system correctly determines the vehicle is towing, the system may be operable to take into account seat occupancy data in determining whether a change in suspension articulation is due to the presence of one or more passengers. Similarly the system may take into account the presence of luggage in a luggage compartment. In some embodiments door opening history may be employed in addition or instead, for example to determine whether a user may have placed luggage in a luggage compartment thereby giving rise to the change in suspension articulation. In addition or instead door opening history may be employed to determine whether one or more passengers may have entered or exited the vehicle.

In some embodiments if an increase in rolling resistance only exceeds a threshold after the system detects a drop in rear ride height, then the system may determine that the vehicle has been coupled to a trailer.

Other strategies are useful and some strategies may be used together in order to increase confidence in the resulting determination.

In some embodiments, if the system detects that the vehicle is towing a trailer prior to key-on, the system may be arranged to store data in respect of the last known rolling resistance of the vehicle for use in determining which subsystem control mode to select immediately after key-on (if the automatic operating condition is selected). If the vehicle comes to rest and is subsequently switched off (key-off) whilst towing a trailer, but following key-on, no trailer is detected (for example because an electrical connection to a trailer cannot be detected), the system may compare current rolling resistance data with last known rolling resistance data. If the data is sufficiently similar the system may determine that the trailer is still being towed.

It is to be understood that in some arrangements, when the system is operating in the automatic selection condition the system may permit the driver to override prevention of selection of one or more subsystem control modes by selecting the manual selection condition. In the manual selection condition the user may select any required mode subject to any further constraints such as selection of an appropriate powertrain gear ratio.

It is to be understood that in some embodiments it may not be possible for the system to make an accurate automated determination whether terrain over which the vehicle is travelling is suited to the sand control mode if vehicle drag increases above a predetermined threshold due to towing. Thus, in some embodiments, when in the automatic selection condition the system is configured not to select the sand subsystem control mode when the system detects that the vehicle is towing.

It is to be understood that in some embodiments if the system is operating in the automatic selection condition the system may be configured to notify the user when operation in one or more control modes has been suspended due to a determination that the vehicle is towing. This is so as to make the user aware of the limited range of control modes available whilst the system is operating in the automatic selection condition. Notification may be made by means of an HMI display and/or any other suitable means including an audible notification.

Additionally or alternatively, the system may be arranged to operate in the manual selection condition only, when it is determined that the vehicle is towing.

In an embodiment, if the system is operating in the automatic selection condition prior to detection of a trailer being coupled to the vehicle, the system may automatically assume the manual selection condition and operate in the SPO (on-road) control mode upon detection of the presence of a trailer.

With reference to the embodiment illustrated in the figures having a switchpack 170 and rotary knob 172, if the system is operating in the automatic selection condition when the presence of a trailer is detected, the rotary knob 172 may be arranged to move from the retracted to the deployed position.

Thus an indication is provided to the user that the automatic selection condition is no longer available, but that the system may be operated in other subsystem control modes according to user selection if required.

In some embodiments, the system may be configured to cancel operation in the automatic selection condition, or limit the available modes when operating in the automatic selection condition, only if a trailer is detected whilst a transmission of the vehicle is in a Park mode (in the case of an automatic transmission), the vehicle is stationary, or the presence of a trailer is detected after the vehicle has been stationary but before the vehicle exceeds a predetermined speed. This feature has the advantage that a change in vehicle behaviour whilst traveling above the predetermined speed due to an automatic change in subsystem control mode may be prevented. Furthermore, if an electrical fault occurs for example in the electrical tow hitch connector and/or associated harness, a probability of an automatic change in system operation during the course of a drivecycle or journey with the trailer still connected is reduced, reducing a risk that driver inconvenience is caused due to the change in vehicle behaviour as a consequence of the electrical fault.

With reference to the accompanying drawings, the vehicle 100 of FIG. 1 is shown in FIG. 5 towing a trailer 195. The trailer 195 is connected to the vehicle 100 by means of a tow hitch or hook 100T of the vehicle 100. The trailer 195 has an electrical service cable 191 that is connectable to a corresponding connector 100C of the vehicle 100. This allows the vehicle to supply power to rear lamps of the trailer 195 such as indicator lamps, brake lamps, license plate illumination and night riding lamps.

The VCU 10 is configured to detect when a trailer service cable 191 is connected by reference to a corresponding signal transmitted over a controller area network (CAN) bus of the vehicle 100. The CAN bus provides a means by which the VCU 10 and subsystem controllers may communicate with one another.

If the VCU 10 is operating in the automatic condition and it is detected that a trailer is connected, the VCU 10 suspends allowance of selection of the sand mode and provides a corresponding alert to the user via the HMI module 32.

In some embodiments the VCU 10 is operable to determine whether the vehicle 100 is towing by reference to data in respect of suspension articulation, ride height, rolling resistance and/or one or more other parameters in addition or instead in the manner described above.

Embodiments of the present invention have the advantage that vehicle composure may be maintained regardless of whether the vehicle is towing a trailer. Operation of the vehicle and associated control systems is also made more intuitive to a user.

Control Mode Memory Management

As described above, in the embodiment of FIG. 1, the VCU 10 is configured wherein an integration process is implemented continually within the selector module 20 to determine whether it is necessary to change from the current control mode to one of the alternative control modes. If the integrated value for one of the alternative control modes reaches the predetermined change threshold before that for the current control mode, the integration process for the current control mode is cancelled and reset to zero and the other alternative control mode, with a higher probability difference, is selected.

In the present embodiment, if the VCU 10 is operating in the automatic mode selection condition at key-off, the VCU 10 stores in a memory thereof the fact that the VCU 10 was in the automatic mode selection condition. Subsequently, at key-on, the VCU 10 resumes operation in the automatic mode selection condition. However, the VCU 10 is arranged to reset to prescribed values the integrated values of the probability that a given control mode is the most suitable mode. In the present embodiment, the prescribed values may be stored in a memory of the VCU 10 and recalled at key-on. Different respective values are recalled in dependence on the control mode in which the VCU 10 resumes operation at key-on. In some alternative embodiments, each of the integrated values may be reset to a value corresponding to a baseline value being the value before any positive values have been integrated, such as a baseline value of substantially zero.

It is to be understood that the moment at which the integrated values are recalled may be any suitable moment prior to commencement of a journey, when a vehicle begins to move over a surface.

In some embodiments, instead of resetting integrated values or other values, a time or distance may be set such that an automatic mode change cannot take place unless a certain time period has expired since the vehicle begins moving or a certain distance must be travelled before an automatic mode change may take place.

In some embodiments, in addition or instead a value of a parameter indicative of terrain type such as coefficient of surface friction (mu) or any other suitable parameter may be set to a prescribed value at key-off, deactivation, key-on or activation. Other parameters may include surface roughness, rolling resistance or any other suitable parameter. In some embodiments the value of the one or more parameters is set to a value that is at or close to a middle of a range of values allowed for that parameter. Thus in some embodiments the value of mu may be set to 0.5 or any other suitable value.

In the present embodiment, the value of mu is set to substantially 0.5 for each control mode in which the VCU 10 may resume operation.

Alternatively, different values of mu may be employed in one or more different control modes.

It is to be understood that a process of choosing the value of the parameters may be undertaken with the intention of delaying a change in control mode once the vehicle 100 commences motion over a surface. The value of the one or more parameters is updated as one or more subsystems 12 of the vehicle 100 gather data in respect of terrain over which the vehicle 100 is moving, and the VCU 10 determines the most appropriate control mode at least in part in dependence on the value of the one or more parameters as described above.

In an embodiment, the VCU 10 is arranged to permanently hold the last selected control mode if a user shifts from a forward gear to a reverse gear, and does not change control mode once the user has selected a forward gear until the vehicle 100 has travelled a predetermined distance (such as around 5 m) to give the VCU 10 time and data samples to re-determine the type of the prevailing terrain.

In an embodiment, the VCU 10 is arranged to store data indicative of a last known gear ratio (transmission range) setting of PTU 137. If at key-on or vehicle activation the gear ratio has changed, the VCU 10 may be configured to ignore the last known control mode and to use a set of default settings for the vehicle sub-systems 12. The default sub-system control settings may correspond to one of the control modes, optionally an on-road control mode such as the SPO mode. This is because a change in selected range indicates the vehicle is most likely about to experience a different use case from that which it had been used in prior to key-off.

In an embodiment, the VCU 10 is arranged to store a last known ride height setting of the suspension system 12 e. If the ride-height has changed due to positive manual intervention by a user (for example by commanding a change in ride-height via user ride height adjustment control 171 cRH (FIG. 5)) whilst being parked, the VCU 10 may be configured to adopt the last known control mode at key-on or vehicle activation. Alternatively, in some embodiments the VCU 10 may be configured to ignore the last known control mode and employ a set of default sub-system control settings or subsystem configuration modes instead. This is because a change in ride height indicates the vehicle is about to experience a different use case from that in which it had been used prior to key-off. The default sub-system control settings may correspond to one of the control modes, optionally an on-road control mode such as the SPO control mode.

In an embodiment, the VCU 10 may be arranged to store data pertaining to one or more parameters, optionally including environmental parameters such as ambient temperature, rain sensor activity, wading sensor activity, tyre pressure monitoring sensor (TPMS) activity and/or one or more other parameters at key off or vehicle deactivation. In some embodiments storing of this data may take place whenever the vehicle transmission 124 is set to PARK. If the VCU 10 determines that values of environmental parameters such as temperature or sensor activity have changed significantly at key-on or by the time the transmission 124 is shifted from PARK to DRIVE or REVERSE or NEUTRAL, the VCU 10 may be configured to ignore the last known control mode and employ a set of default sub-system control settings. The default sub-system control settings may correspond to one of the control modes, optionally an on-road control mode such as SPO mode as described above.

It is to be understood that this has the advantage for example that if the temperature falls significantly overnight, the VCU 10 can adapt to the likelihood of there being snow around the vehicle 100 at key-on even though the ground may have been clear of snow at key-off.

Monitoring the readings from TPMS sensors in each wheel may permit the VCU 10 to identify when a driver has raised or lowered all four tyre pressures together whilst the vehicle 100 was parked, indicative of the driver preparing to operate the vehicle 100 in a different use case or operational situation compared with that which was the case before the vehicle 100 was parked. In some embodiments, if a change in tyre pressure of one or more wheels of more than a prescribed amount is present at key-on or vehicle activation, the VCU 10 may commence operation in a default mode such as SPO.

Some embodiments of the present invention allow the VCU 10 more time to obtain data in respect of prevailing terrain conditions when a vehicle 100 first starts moving. This increases a confidence with which the VCU 10 may command a change in selected control mode when it is determined that a change in control mode is required.

Embodiments of the present invention help to ensure that operation of the VCU 10 in respect of the performance of automatic mode changes is as imperceptible as possible to a user. Embodiments of the invention have the advantage of reducing the chance that unnecessary control mode changes take place at the beginning of a journey.

In some embodiments, the VCU 10 may be arranged to determine the control mode in which it is to be operated at key-on or vehicle activation in dependence at least in part on an amount of time that has elapsed since key-off or vehicle deactivation. In some embodiments, instead of commencing operation in the same control mode as that in which operation was last terminated, i.e. the control mode in which the VCU 10 was operating at key-off or vehicle deactivation, the VCU 10 may assume a default mode if the amount of time since key-off or vehicle deactivation exceeds a prescribed time period. The time period may be a period of 1 hour, 5 hours, 10 hours or any other suitable period. In the present embodiment the prescribed time period is a period of 6 hours. The default mode may be assumed after a prescribed period of time in dependence on the selected mode. For example, for certain modes the VCU 10 may commence operations at key-on or vehicle activation in the same mode as that in which operations were terminated regardless of the length of time that has elapsed since key-off or vehicle deactivation. In the present embodiment, if the VCU 10 was in the GGS or SPO modes at key-off or vehicle deactivation, the VCU 10 recommences operation in the GGS or SPO modes regardless of the amount of time that has elapsed since key-off or vehicle deactivation.

In some embodiments, the VCU 10 may be configured to adopt a control mode at key-on or vehicle activation in dependence on the amount of time that has elapsed since key-off or vehicle deactivation such that the VCU 10 may commence operations in either (a) the mode in which it was operating at key-off or vehicle deactivation; (b) a first default mode once a first prescribed period has elapsed; and (c) a second or further default mode once a second or further prescribed period has elapsed. The first, second and any further default mode may be selected in dependence on the control mode in which the VCU 10 was operating at key off or vehicle deactivation.

Thus for example if the VCU 10 was operating in the MR control mode at key-off or vehicle deactivation, then at key-on or vehicle activation within the first prescribed period the VCU 10 may assume the MR mode. After the first prescribed period has elapsed the VCU 10 may assume the GGS mode. The VCU 10 may assume the GGS mode regardless of the amount of time that elapses once the first period has elapsed. Alternatively, in some embodiments the VCU 10 may assume the SPO mode after a second prescribed period has elapsed, such as a period of 12 hours. Other time periods are also useful.

In the case the VCU 10 has been operating in the sand mode, the VCU 10 may be configured to assume the SPO mode after a first prescribed period has elapsed, such as a period of 6 hours. The VCU 10 may be configured to resume operation in the SPO mode regardless of the length of time that elapses after the first prescribed period has elapsed.

FIG. 7 illustrates a method of operation of a vehicle 100 according to an embodiment of the present invention.

The method may commence on starting point S1 or starting point S2 or at any other suitable starting point.

Commencing at starting point S1, at step S101 the VCU 10 is operating in the automatic vehicle control mode selection condition with the engine 121 switched on and the transmission 124 in a forward driving mode. The VCU 10 then continues at step S103.

At step S103 the VCU 10 checks whether the vehicle 100 has assumed a key-off condition, or has been deactivated by assuming a Park or Neutral mode of the transmission 124 from a driving mode. If the vehicle 100 has not assumed the key-off condition or been deactivated, the VCU 10 repeats step S103, otherwise the VCU 10 continues at step S105. In some embodiments the VCU 10 continues at step S105 only if the key-off condition has been assumed. In some alternative embodiments the VCU 10 continues at step S105 only if the Park or Neutral modes are assumed by the transmission 124. In some embodiments if a driver does not place the transmission 124 in park before key-off the VCU 10 causes the transmission 124 to assume the Park mode automatically following key-off. Other arrangements are also useful.

At step S105 the VCU 10 stores data corresponding to the current control mode and time. The current time may be stored in any prescribed units, for example units of 5 minutes, 30 minutes, 60 minutes or any other suitable units. In some embodiments, instead of storing a current time the VCU 10 may reset or otherwise start a timer. The VCU 10 then continues at step S107.

At step S107 the VCU 10 determines whether the vehicle 100 has assumed a key-on condition or been reactivated by assuming a forward drive mode of the transmission 124. It is to be understood that the forward drive mode be a Drive mode and/or any other suitable mode. If at step S107 it is determined that the vehicle 100 has not assumed the key-on condition or been reactivated, the VCU 10 repeats step S107. Otherwise the VCU 10 continues at step S109.

It is to be understood that in some embodiments, the VCU 10 does not perform literal repeated checks at step S107 following key-off. Rather, at key-on, the VCU 10 is caused to execute step S109, for example as of a set of checks performed when the VCU 10 is initialised following key-on.

At step S109 the VCU 10 determines by reference to the data stored at step S105 whether the amount of elapsed time since key-off or deactivation exceeds a first prescribed value. If the amount of elapsed time does not exceed the first prescribed value the VCU 10 continues at step S111, otherwise the VCU 10 continues at step S113.

At step S111 the VCU 10 retrieves the data stored at step S105 in respect of the identity of the control mode in which the vehicle 100 was operating. The VCU 10 resets the integrated values of the probability that a given control mode is the most suitable mode to substantially zero, and then commences operation in the control mode in which the vehicle was operating as determined according to the retrieved data. The VCU 10 then continues at step S101.

As noted above, if at step S109 the VCU 10 determines that the elapsed time exceeds the first prescribed value the VCU 10 continues at step S113. At step S113 the VCU 10 commences operation in the default (SPO) control mode. The VCU 10 then continues at step S101.

Embodiments of the present invention have the advantage that vehicle composure and driver confidence may be enhanced. In some embodiments this is at least in part because a vehicle 100 is controlled in such a manner that a change in control mode of a control system immediately following launch of a vehicle may be delayed, allowing a driver to gain familiarity with one or more vehicle handling characteristics before a change in control mode takes place.

Furthermore, in some embodiments a control system may anticipate changes in driving surface and adopt a different control mode at or before vehicle launch compared with that in which the vehicle ceased operating at the previous key-off or vehicle deactivation.

Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. 

The invention claimed is:
 1. A motor vehicle control system for selecting a driving surface and for controlling a plurality of vehicle subsystems to operate in a plurality of subsystem control modes in dependence on the selected driving surface, the system being operable in a manual control mode selection condition in which a user is able to select said driving surface and an automatic control mode selection condition in which the system is configured to select said driving surface automatically, wherein the vehicle control system is provided with a processor and memory arranged to memorize a last selected control mode that was selected prior to vehicle de-activation or key-off when operating in the automatic control mode selection condition, and upon the next subsequent vehicle activation or key-on, the system is configured to continue operating in the memorized control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place.
 2. A system according to claim 1 wherein when operating in the automatic control mode selection condition, the system is configured to select the most appropriate subsystem control mode by: (1) for each type of control mode, calculating the probability that the control mode is suitable for the terrain or driving surface over which the vehicle is travelling, based on a plurality of terrain indicators, the terrain indicators being determined according to the value of one or more vehicle operating parameters; (2) integrating positive differences between the probability for the current control mode and that for each of the other control modes; and (3) when the integrated value of the positive differences between the current control mode and one of the other control modes exceeds a pre-determined threshold, assuming that control mode.
 3. A system according to claim 2 arranged wherein at vehicle activation or key-on the system is configured to set the integrated value of the positive differences for each control mode to a respective prescribed value.
 4. A system according to claim 2 configured to set at least one of the plurality of terrain indicators to a prescribed value at key-off, vehicle deactivation, key-on or vehicle activation.
 5. A system according to claim 4 wherein the prescribed value is a value that is at or close to a middle of a range of values allowed for that parameter before a threshold for change of control mode is triggered.
 6. A system according to claim 4 wherein the at least one terrain indicator includes a value of surface coefficient of friction between a wheel and a driving surface and wherein the value of surface coefficient of friction is set to a value of substantially 0.5 at key-off, vehicle deactivation, key-on or vehicle activation.
 7. A system according to claim 1 arranged to memorize the last selected control mode in response to key-off or vehicle deactivation.
 8. A system according to claim 1 wherein memorising the last selected control mode prior to vehicle deactivation includes memorising the last selected control mode when a transmission of the vehicle is placed into a PARK or NEUTRAL mode.
 9. A system according to claim 1 arranged wherein a transition from PARK or NEUTRAL to a forward drive mode is considered to be a vehicle activation.
 10. A system according to claim 1 arranged to remain in the last selected control mode if a user shifts from a forward gear to a reverse gear, wherein when a user shifts from a forward gear to a reverse gear the system is configured to remain in the last selected control mode until a forward gear is subsequently selected.
 11. A system according to claim 10 wherein when the forward gear is subsequently selected the system is configured to remain in the last selected control mode until the vehicle has travelled a predetermined distance, or a predetermined time has elapsed.
 12. A system according to claim 1 arranged at key off or vehicle deactivation to store data indicative of a last known gear ratio of a range transmission, wherein if at key-on or vehicle activation the gear ratio of the range transmission has changed in comparison to the stored data, the system is configured to assume a set of default settings for the vehicle sub-systems.
 13. A system according to claim 1 arranged at key off or vehicle deactivation to store data indicative of a last known ride height setting of a suspension system, wherein if at key-on or vehicle activation the ride height setting of a suspension system is determined to have changed, the system is configured to assume a set of default settings for the vehicle sub-systems.
 14. A control system according to claim 1 wherein the control modes are control modes of at least one subsystem of a vehicle, the system comprising a subsystem controller for initiating control of the or each of the vehicle subsystems in the selected one of the plurality of subsystem control modes, each of which subsystem control modes corresponds to one or more different driving surfaces; and wherein the control modes are control modes of at least two vehicle subsystems selected from amongst an engine management system, a transmission system, a steering system, a brakes system and a suspension system, and in each system operating mode the system is configured to cause each one of a plurality of vehicle subsystems to be operated in a subsystem configuration mode appropriate to the driving surface, wherein the control modes include one or more of: control modes of a suspension system and the plurality of subsystem configuration modes comprise a plurality of ride heights; control modes of a fluid suspension system in which fluid interconnection can be made between suspensions for wheels on opposite sides of the vehicle, and wherein said plurality of subsystem configuration modes provide different levels of said interconnection; control modes of a steering system which can provide steering assistance, and wherein said plurality of subsystem configuration modes provide different levels of said steering assistance; control modes of a brakes system which can provide braking assistance, and said plurality of subsystem configuration modes provide different levels of said braking assistance; control modes of a brake control system which can provide an anti-lock function to control wheel slip, and said plurality of subsystem configuration modes allow different levels of said wheel slip; control modes of a traction control system which is arranged to control wheel spin, and said plurality of subsystem configuration modes allow different levels of said wheel spin; control modes of a yaw control system which is arranged to control vehicle yaw, and said plurality of subsystem configuration modes allow different levels of divergence of said vehicle yaw from an expected yaw; control modes of a range change transmission and said subsystem configuration modes may include a high range mode and a low range mode of said transmission; control modes of a powertrain system which includes a powertrain controller and an accelerator or throttle pedal, the subsystem configuration modes providing different levels of responsiveness of the powertrain controller to movement of the accelerator or throttle pedal; and control modes of a transmission system operable in a plurality of transmission ratios and including an electronic transmission controller arranged to monitor at least one parameter of the vehicle and to select the transmission ratios in response, and wherein the subsystem configuration modes include a plurality of transmission configuration modes in which the transmission ratios are selected differently in response to said at least one parameter.
 15. A system according to claim 1 configured to select a control mode in which the vehicle is to operate upon vehicle activation or key-on in dependence at least in part on an amount of time that has elapsed since vehicle deactivation or key-off, wherein if the amount of elapsed time exceeds a first prescribed value the system is configured to assume a first prescribed control mode upon vehicle activation or key-on.
 16. A system according to claim 15 wherein the first prescribed control mode is determined in dependence at least in part on the control mode in which the vehicle last operated at key-off or vehicle deactivation.
 17. A system according to claim 1 configured to continue operating in the memorized control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place by suspending changes in operating mode following commencement of movement of a vehicle over a surface when the system is in the automatic operating mode selection condition for a prescribed period of time or for a prescribed distance of travel since movement was commenced.
 18. A method of controlling a motor vehicle implemented by a control system provided with a processor and memory, the method comprising selecting a driving surface and controlling a plurality of vehicle subsystems to operate in a plurality of subsystem control modes in dependence on the selected driving surface, whereby in a manual control mode selection condition, selecting the driving surface comprises selecting the driving surface by reference to a user input in respect of the driving surface; and in an automatic control mode selection condition, selecting the driving surface comprises the processor selecting said driving surface automatically, wherein the method comprises storing in the memory of the system a last selected control mode that was selected prior to vehicle de-activation or key-off, and upon the next subsequent vehicle activation or key-on, continuing to operate in the same control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place.
 19. A non-transient carrier medium carrying computer readable code executable by a vehicle control system comprising a processor and a memory, wherein, when executed by the vehicle control system, the code causes a vehicle to carry out a method comprising the following steps: selecting a driving surface and controlling a plurality of vehicle subsystems to operate in a plurality of subsystem control modes in dependence on the selected driving surface, whereby in a manual control mode selection condition, selecting the driving surface comprises selecting the driving surface by reference to a user input in respect of the driving surface; and in an automatic control mode selection condition, selecting the driving surface comprises the processor selecting said driving surface automatically, wherein the method comprises storing in a non-transitory computer readable memory a last selected control mode that was selected prior to vehicle de-activation or key-off, and upon the next subsequent vehicle activation or key-on, continuing to operate in the same control mode and to automatically obtain new data in respect of a driving surface over which the vehicle is moving before allowing a change in control mode to take place.
 20. A vehicle comprising a system according to claim
 1. 